Among image forming apparatuses provided with developing cartridges, there is known an image forming apparatus capable of determining whether a developing cartridge is attached to the apparatus or capable of identifying specifications of the developing cartridge. For example, prior art discloses an image forming apparatus includes a sensor for detecting a protrusion of a detection gear provided at a developing cartridge, and the image forming apparatus determines whether the developing cartridge is attached to the image forming apparatus or not.
Further, prior art also discloses an image-forming device including a developing electrode and a supply electrode. The developing electrode is a bearing for the developing roller, and the supply electrode is a bearing for the supply roller. The developing electrode and supply electrode contact corresponding electrodes in the image-forming device in the axial direction of the developing roller.
Further, prior art also discloses an image-forming apparatus including a detection gear and a developing electrode. The detection gear and the developing electrode are positioned at a same side in an axial direction of a developing roller.